Booster antenna structure for a chip card

ABSTRACT

In various embodiments, a booster antenna structure for a chip card is provided, wherein the booster antenna structure may include a booster antenna; and an additional electrically conductive structure connected to the booster antenna.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to German Patent Application Serial No.10 2011 056 323.7, which was filed Dec. 13, 2011, and is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

Various embodiments relate to a booster antenna structure for a chipcard.

BACKGROUND

In the case of normal chip cards which are widely used, for example inelectronic payment transactions, the communication between the chiplocated on the chip card and a reader is contact-based, i.e. via chipcard contacts exposed toward the outside of the chip card. For thispurpose, however, the chip card must always be singled out when used andintroduced into a corresponding reader which may be considered to bedisruptive by a user. An interesting extension which solves the problemis offered by so-called dual interface chip cards in which the chip canalso communicate by means of a contactless interface in addition to thenormal contact-based interface. The contactless interface on the chipcard can have a chip card antenna which is contained in the chip cardand connected to the chip. The chip card antenna and the chip can bearranged conjointly on a chip card module wherein such a miniaturizedform of the chip card antenna can then be called a chip card moduleantenna. Independently of the type of chip card antenna, an electricalconnection is formed between it and the chip card module or the chip,respectively.

In the case of electronic payment systems, for example, a functionaldistance of up to 4 cm is required between the chip and the readingunit. However, meeting this target specification may be found to beproblematic since it may not be possible in some cases to arrange asufficiently large chip card module antenna on the small surfaceavailable on the chip card module for wireless communication to takeplace at the required distance. In order to improve the wirelesscommunication capability, a further antenna can be provided in additionto the chip card module antenna, namely an amplifier antenna or boosterantenna. The booster antenna can be provided on a separate layer andcontained in the chip card. The separate layer which contains thebooster antenna can be laminated into the chip card, for example, duringits production.

In the case of chip card antennas which are not arranged on the chipcard module and therefore have in most cases an adequate size, the useof a booster antenna can be omitted. When completed chip card bodies areequipped with chip card modules, however, the chip card must then bemilled precisely so that the contacts provided on the chip card modulecan be positioned over corresponding contacts of the chip card antenna.The contacts can then be joined together by means of an adhesive,supplying pressure.

The production process described above is costly and complex. Inaddition, the contact locations between chip card module and the chipcard antenna can have little mechanical ruggedness and may becomedetached in the case of bending and folding processes to which chipcards can be exposed in everyday use. Having regard to these problems,the expected life of a chip card having a chip card antenna may be twoyears. In general, a far longer life of, for example, ten years would bedesirable, for instance when such chip cards are used in governmentalfacilities where the costs of exchanging or renewing due to the volumeof chip cards used could be saved.

To avoid the problems of the mechanically susceptible electricalconnection with the chip card module or the chip, respectively, existingin the case of large-format chip card antennas, booster antennas arecoupled inductively to chip card module antennas. Normal boosterantennas extend in most cases over the entire surface of the chip card,if necessary also over part-areas which are provided, for example, forlettering embossed in the chip card (embossing areas, defined, forexample, in ISO/IEC 7811-1 Standard) or are provided for the chip cavityso that such chip cards are basically not ISO/IEC-compliant.Furthermore, there has hitherto not been any optimization of the boosterantenna in chip cards with regard to their electrical parameters so thatsuch chip cards cannot be certified, for example, according to the EMVCoStandard—a global standard for credit and ATM cards on the basis of chipcard technology.

SUMMARY

In various embodiments, a booster antenna structure for a chip card isprovided, wherein the booster antenna structure may include a boosterantenna; and an additional electrically conductive structure connectedto the booster antenna.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. The drawings are not necessarilyto scale, emphasis instead generally being placed upon illustrating theprinciples of the invention. In the following description, variousembodiments of the invention are described with reference to thefollowing drawings, in which:

FIG. 1 shows an exemplary chip card module with chip card module antennafor a chip card;

FIG. 2A shows a transmission system having a reading unit and a chipcard module with chip card module antenna without booster antennastructure;

FIG. 2B shows a transmission system having a reading unit and a chipcard module with chip card module antenna and with a booster antennastructure according to various embodiments;

FIG. 3 shows a diagram for illustrating the influence of the number ofturns of the booster antenna structure according to various embodimentson the voltage induced in the chip card module antenna;

FIGS. 4A to 4F show various contactless chip card module arrangementsfor forming the inductive coupling area according to the variousembodiments;

FIG. 5 shows a section of an embodiment of an inductive coupling area;

FIG. 6 shows a diagram for illustrating the dependence of a couplingfactor on the distance between turns of the chip card module antenna andbooster antenna turns;

FIG. 7 shows a section of a booster antenna structure according tovarious embodiments;

FIG. 8A shows a section of a contactless chip card module arrangementaccording to various embodiments;

FIG. 8B shows a section of a further contactless chip card modulearrangement according to various embodiments;

FIG. 9 shows a circuit diagram of a system of reading unit and acontactless chip card module arrangement according to variousembodiments;

FIG. 10 shows a circuit diagram of a system of a contactless chip cardmodule arrangement according to various embodiments;

FIG. 11A shows a booster antenna structure according to variousembodiments with a finger capacitor;

FIG. 11B shows an enlarged view of the finger capacitor shown in FIG.11A;

FIG. 12A shows a booster antenna structure according to variousembodiments with a spiral capacitor;

FIG. 12B shows a booster antenna structure according to variousembodiments with a dummy turn as capacitor;

FIG. 13A shows a top of a booster antenna structure according to variousembodiments;

FIG. 13B shows a bottom of a booster antenna structure according tovarious embodiments;

FIG. 13C shows an overlaid view of the top of the booster antennastructure from FIG. 13A and the bottom of the booster antenna structurefrom FIG. 13B;

FIG. 14 shows an image of a booster antenna structure, produced by meansof an electroplating process, according to various embodiments; and

FIG. 15 shows an image of a booster antenna structure, produced by meansof an etching process, according to various embodiments.

DESCRIPTION

The following detailed description refers to the accompanying drawingsthat show, by way of illustration, specific details and embodiments inwhich the invention may be practiced.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration”. Any embodiment or design described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments or designs.

The word “over” used with regards to a deposited material formed “over”a side or surface, may be used herein to mean that the depositedmaterial may be formed “directly on”, e.g. in direct contact with, theimplied side or surface. The word “over” used with regards to adeposited material formed “over” a side or surface, may be used hereinto mean that the deposited material may be formed “indirectly on” theimplied side or surface with one or more additional layers beingarranged between the implied side or surface and the deposited material.

In the detailed description which follows, reference is made to theattached drawings which form a part of it and in which, for the purposeof illustration, specific embodiments are shown in which the inventioncan be exercised. In this regard, directional terminology such as, forinstance, “top”, “bottom”, “front”, “rear”, etc. are used with referenceto the orientation of the figure(s) described. Since components ofembodiments can be positioned in a number of different orientations, thedirectional terminology is used for illustration and is in no wayrestrictive. Naturally, other embodiments can be used and structural orlogical changes can be performed without deviating from the range ofprotection of the present invention. Naturally, the features of thevarious embodiments described herein can be combined with one anotherunless specified differently specifically. The detailed descriptionwhich follows should, therefore, not be considered in a restrictivesense and the protective range of the present invention is defined bythe attached claims.

Within the framework of the present description, the terms “linked”,“connected” and “coupled” are used for describing both a direct and anindirect link, a direct or indirect connection and a direct or indirectcoupling. In the figures, identical or similar elements are providedwith identical reference symbols as far as this is appropriate.

FIG. 1 shows a section of a rear of a chip card module 100 including achip card module antenna with which a booster antenna structureaccording to various embodiments may be coupled. The rear of the chipcard module 100 may be understood to be the side which is arrangedopposite the side of the chip card module on which the chip cardcontacts are arranged and is thus not visible from the outside afterinsertion of the chip card module into a chip card body. The chip cardmodule 100 has a carrier 112 on which an integrated circuit in the formof the chip 102 is arranged. As in the embodiment of the chip cardmodule 100 shown, the carrier 112 may be at least partially transparentso that the chip card contacts 114 which are arranged on the front ofthe carrier 112 are also visible from the rear of the chip card module100. The chip card contacts 114 are coupled to the chip 102 by means ofwiring 110. At the rear of the carrier 112 an off-chip coil 104 isprovided and has thirteen turns in the present embodiment. The turns ofthe off-chip coil 104 are arranged in a ring around the chip 102. Eachof the coil turns has an almost square or rectangular shape with roundedcorners, the left-hand side having in the present embodiment a kink 116,i.e. a course deviating from a straight line. The kink 116 has theeffect that the coil turns are offset toward the center of the off-chipcoil 104 and thus an area is created at the outer edge of the coil 104at which, for example, an end contact 106 of the coil may be arranged.The design of the off-chip coil 104 may be adapted to other componentspresent on the carrier 112 as required. The shape of the coil turns maynaturally deviate from the shape shown in FIG. 1 and have, for example,other kinks. The off-chip coil 104 has at its outer end the end contact106. The end contact 106 is conducted to the front of the carrier 112 bymeans of a passage and is connected to a contact bridge 118. The contactbridge 118, which is arranged on the front of the carrier 112, iscoupled to a further passage which is connected to a further contact 108which, in turn, is coupled to the chip 102. In this manner, the off-chipcoil 104 may be closed without an additional plane having to be built upon the rear of the carrier 112 in which a line could run which crossesthe coil turns. The off-chip coil 104 shown in FIG. 1 is a unilateralmodule antenna, wherein a contact bridge 118 is used on the side of thechip card contacts 112 in order to close the off-chip coil 104. The chip102 arranged on the carrier 112 may have, for example, an internalcapacitor of approximately 40 pF to 100 pF, for example in the range ofabout 50 pF to 80 pF. The turns of the off-chip coil 104 may have, forexample, silver, aluminum, copper, gold and/or conductive alloys and mayhave a conductor track width of at least 40 μm which can be, forexample, about 60 μm, about 80 μm or about 100 μm or about up to 200 μm.The turns of the off-chip coil 104 may be arranged, for example, at adistance of about 80 μm from one another on the carrier 112. Bothparameters—conductor track width and conductor track spacing—areparameters which can be adapted with regard to the inductance of theoff-chip coil 104 to be achieved.

The chip card module 100 shown in FIG. 1 is a so-called CoM (coil onmodule) which has the chip and a coil, the coil handling the function ofan antenna and providing for contactless communication between the chipand a reading unit. The chip card module 100 may be a dual interfacechip card module so that the chip can communicate with a reading unit bymeans of a contact-connected interface (by means of contacts 114) and bymeans of a contactless interface (off-chip coil 104). The contactlesschip card module according to various embodiments, for example acontactless chip card module of a dual interface chip card, has aresonant circuit which may essentially have the chip and the off-chipcoil and can be operated independently. The resonant frequency of theresonant circuit ay be set to the operating frequency of the chip inthis arrangement and be, for example, approximately 13.56 MHz, thisfrequency corresponding to one of the frequencies of the RFID(radio-frequency identification) standard in the short-wave band.

FIG. 2A shows a system 200 of reading unit 202 and chip card module 206with chip card module antenna, but without booster antenna structure.The contactless communication (often also called near-fieldcommunication) between reading unit 202 and chip card module 206 isbased on electromagnetic waves (for example on one or more magneticfields), wherein an antenna 204 of the reading unit 202, which can beconstructed as a coil, and the off-chip coil arranged on the chip cardmodule 206 are used for transmitting these. In the transmission ofsignals between reading unit 202 and chip card module 206, a currentflow is induced in the chip card module antenna of the chip card module206 by a clocked magnetic field of the reading unit 202. In the chipcard module 206, a load resistance is switched on and off at the clockrate of the signal, which is to be transmitted. This load modulationcauses a change in the current flow through the chip card moduleantenna, which in turn results in a changing reaction of the chip cardmodule antenna to the amplitude of the magnetic field of the reader 202.The modulation of the magnetic field of the reader, caused by the loadmodulation in the chip card module, can be detected in the reader. Inorder to improve the performance of the contactless communication of achip card module, an amplifier antenna (also called booster antenna) canbe coupled additionally to the chip card module. FIG. 2B shows a system220 of reading unit 202 and chip card module 206 with chip card moduleantenna and with booster antenna structure 208 according to variousembodiments. The booster antenna structure 208 acts as an amplifyingintermediary, as it were, between the antenna 204 of the reading unit202 and the off-chip coil of the chip card module 206. The boosterantenna structure 208 has larger turn structures than the off-chip coiland is, therefore, capable of stronger or better coupling to themagnetic field emanating from the antenna 204 of the reading unit 202.The booster antenna structure 208 is coupled to the off-chip coilarranged on the chip card module 206 by means of the at least oneinductive coupling area 210, i.e. no electrical or bodily contact isrequired between the circuit which has the off-chip coil and the boosterantenna structure 208. The inductive coupling area 210 can have, forexample, coupling turns which surround the chip card module 206 and thusthe off-chip coil, the coupling turns being coupled out of the turns ofthe booster antenna 208. Due to the spatial proximity of the turns ofthe off-chip coil to the coupling turns of the booster antenna 208,electromagnetic coupling can be achieved between the two coils, i.e. onecoil can induce currents in the other one. Other embodiments of the atleast one inductive coupling area will be explained later.

The coupling or intensity of coupling, respectively, between a chip cardmodule and a booster antenna is an essential component of thecontactless performance of an overall system which essentially has thechip card and the reading unit and can be described quantitatively by acoupling factor or coupling parameter, respectively. The number of turnsof the booster antenna and the distance between the turns of the boosterantenna and the turns of the off-chip coil are important settingparameters in this context, as is the size of the area of overlap of theturns.

The effect which the booster antenna or booster antenna structure has onthe voltage induced in the chip card module antenna or in the circuit onthe chip card module by an electromagnetic field of a reading unit isillustrated in the diagram 300 shown in FIG. 3. In the diagram 300, thenumber of turns of a booster antenna is plotted according to variousembodiments along the x axis 302. This number of turns can relate to theturns which are larger than the optional coupling turns which mayenclose the at least one inductive coupling area. In the embodimentshown in FIG. 2, the booster antenna 208 has two turns and there is aninductive coupling area 210 which is enclosed or edged by two couplingturns, the coupling turns being coupled out of a turn of the boosterantenna. In such embodiments, the number of turns is independent of thenumber of coupling turns. Along the y axis 304, the voltage is plottedwhich can be induced at the chip and/or the circuit on the chip cardmodule by the electromagnetic field of a reading unit located in thevicinity of the contactless chip card module arrangement according tovarious embodiments. The graph 306 in the diagram 300 illustrates thatwith an increasing number of turns of the booster antenna, the inducedvoltage also increases. However, the gain in voltage per additional turndecreases with an increasing number of turns which is reflected in arise in the graph 306 decreasing toward greater numbers of turns.

The number of turns of the booster antenna may be limited by theavailable space. In principle, the booster antenna structure may extendto the area which is limited, for example, by the size of a chip card.In this context, the booster antenna structure can be arranged as alayer within the chip card, for example laminated in, considering, forexample, all sizes of chip cards which are contained in the ISO/IEC 7810Standard. Furthermore, process parameters, for example choice ofmaterial, thickness of turn conductor tracks and/or geometry of theturns can be taken into consideration in the selection of the optimumnumber of turns.

When designing the geometry of the booster antenna, restrictions mayoccur. For example, the ISO/IEC 7811-1 Standard specifies areas for achip card in the ID-1 format (ID-1, as one of the chip card formats, isspecified in ISO/IEC 7810 Standard) which are not available for thebooster antenna. These may be, for example, areas for embossing and/orthe area which is covered by the chip card module. Due to theserestrictions, the design for achieving optimum coupling between chipcard module and booster antenna may be restricted. Too small a number ofturns of the booster antenna may result, for example, in suboptimalcoupling. If these boundary conditions just mentioned and also containedin the Standard are neglected, improved coupling may be achieved but thecorresponding chip cards do not then comply with the ISO/IEC 7811-1Standard and cannot be used, for example, where embossing plays a role.

The booster antenna structure according to various embodiments followsthe approach of estimating the areas available for the design of thebooster antenna structure, taking into consideration the respectiveprocess parameters for producing the booster antenna structure such as,for example, choice of material, thickness of the turn conductor tracksand/or geometry of the turns. This makes it possible to determine anoptimum number of turns of the booster antenna.

In general, a booster antenna structure may be produced, for example, bymeans of a printing process or of an etching process. In variousembodiments, the booster antenna structure can also be installed orproduced by galvanizing. Contactless systems of chip card and readingunit can be formed in various manners but they are all subject tosimilar requirements due to their application.

The electrical requirements are given by the ISO/IEC 14443 Standard,ISO/IEC 10373-6 Standard and the EMVCo Standard (EMVCo: EMV Standard forcontactless chip cards; EMV: global standard for credit and ATM cardsbased on chip card technology), for example the EMV contactlesscommunication protocol specification version 2.0.1, July 2009. Oneimportant requirement is the minimum operating field strength, that isto say the minimum field strength at which a correct signal transmissioncan occur between chip card and reader (and conversely). The minimumload modulation amplitude (LMA) is also of significance. This parameterdescribes a magnetic field amplitude achievable by means of the loadmodulation described above, which may effect a change in the magneticfield of the reader within the normal operating range. A furtherimportant aspect is the maximum loading effect which relates to thereaction of the chip card on the reader. The chip card is operated bythe electromagnetic field of the reader and, in turn, generates its ownelectromagnetic field which, in turn, loads the reader. The maximumreaction defines an upper limit for this loading effect so that thereader can still operate correctly.

Further demands on booster antenna structures relate to their mechanicalcharacteristics. Thus, the booster antenna structures must be embeddablein the chip cards, i.e. the size of the respective chip card in which abooster antenna structure is used determines the boundaries for apossible dimension of the booster antenna structure. Possible sizes ofchip cards may be obtained, for example, from the ISO/IEC 7810 Standard.Furthermore, the design or the shape of the booster antenna itself maybe subject to spatial restrictions within the chip card which mayresult, for example, from areas to be kept free, for example forembossed lettering as specified in the ISO/IEC 7810-11 Standard.

In this context, the production process of the booster antenna structuremay run iteratively in accordance with various embodiments. Test modelsmay be produced, surveyed and specified and various parameters may besubsequently adapted for meeting the requirements.

An enlargement of the booster antenna, i.e. an enlargement of the areaenclosing the booster antenna has a positive effect on the minimum loadmodulation amplitude and the minimum operating field strength since thecoupling between the reading unit and the booster antenna is increased.At the same time, however, the reaction of the chip card on the readingunit is increased. Generally, a size of the booster antenna may beselected to be such as is allowed in accordance with the correspondingrestrictions or specified conditions.

In most cases, enlarging the number of turns of the booster antenna maylead to a lower minimum operating field strength. However, this positiveeffect is reduced with an increasing total number of turns alreadypresent in the booster antenna, as can be seen in the diagram 300 inFIG. 3 (increasingly shallower graph 306 in diagram 300 in FIG. 3). Atthe same time, however, the achievable minimum load modulation amplitudeis reduced with an increasing number of turns of the booster antenna. Asa compromise solution, a reasonable number of turns of the boosterantenna can be within a range of about two to about five and be, forexample, four turns in chip cards in the ID-1 format. Since the couplingparameter or the strength of coupling between the booster antenna andthe chip card module or its antenna, respectively, may be changedwithout significantly influencing other component parameters, itrepresents a good parameter for aligning the entire system.

FIG. 4A to FIG. 4F show different contactless chip card modulearrangements 400, 410, 420, 430, 440, 450 according to variousembodiments for forming the inductive coupling area. In each of thefigures mentioned, a booster antenna structure 402 is shown, with onlythe booster antenna being shown, and a chip card module 404 which has anoff-chip coil 406 and a chip (not shown separately). The booster antenna402 is only shown by a line since the geometric arrangement of theoff-chip coil 406 of the chip card module 404 with respect to thebooster antenna 402 is the focal point of the explanation in FIG. 4A toFIG. 4F. Naturally, the booster antenna structure 402 may have more thanone turn, for example two, three, four or more turns, and othercomponents such as capacitors or resistors. In each of FIG. 4A to FIG.4F, the at least one inductive coupling area is formed by the proximityof the chip card module 404 to the booster antenna. In other words, theat least one inductive coupling area coincides spatially with thelocation of the chip card module 404. In the embodiments of thecontactless chip card module arrangement shown in FIG. 4A to FIG. 4F,the turns of the off-chip coil 406 are arranged to form an approximatelysquare or rectangular shape having rounded corners. In variousembodiments, the sides can deviate from a straight course (see alsoFIG. 1) and/or the off-chip coil 406 may assume other geometric shapes.

In FIG. 4A, an inductive coupling between the booster antenna 402 andthe off-chip coil 406 is achieved by the off-chip coil being arranged insuch a manner that two sides of the off-chip coil 406 extend over theirentire length adjoining and essentially in parallel with the turns ofthe booster antenna 402. In this arrangement, the off-chip coil 406 isarranged in an outer corner area of the booster antenna 402, i.e. in onecorner of the booster antenna 402, and outside an area which is borderedby the turn (or turns) of the booster antenna 402 which is subsequentlycalled booster antenna area. Using geometries of this type, couplingparameters of the order of magnitude of up to 0.1 can be achieved independence on the number of turns of the booster antenna 402 and thedistance between these and the off-chip coil 406. The contactless chipcard module arrangement 400, shown in FIG. 4A, according to variousembodiments, may be used if an enclosure of the off-chip coil 404 by thebooster antenna 402 is not possible, for example due to areas which arereserved for embossed lettering.

In FIG. 4B, just as in FIG. 4A, two sides of the off-chip coil 406extend over their entire length adjoining and essentially in parallelwith parts of the booster antenna 402, but the chip card module 404 isarranged here within the booster antenna area. In other words, the chipcard module 406 is arranged in an inner corner area of the boosterantenna 402. In comparison with the contactless chip card modulearrangement 400 shown in FIG. 4A, the contactless chip card modulearrangement 410 shown in FIG. 4B has a larger coupling parameter, i.e.the booster antenna 402 is coupled better to the off-chip coil 406there.

In the exemplary contactless chip card module arrangement 430 shown inFIG. 4C, the chip card module 406 is arranged within the booster antennaarea, only one side of the chip card module 404 being arrangedimmediately adjoining the booster antenna 402. Regarding FIG. 5 and thediagram 600 shown in FIG. 6, immediately adjoining may be understood tobe a distance between a turn of the off-chip coil 406 and a turn of thebooster antenna of from up to 10 mm in various embodiments.

The exemplary contactless chip card module arrangement 440 shown in FIG.4D corresponds essentially to the exemplary contactless chip card modulearrangement 410 shown in FIG. 4B, the distance between the off-chip coil406 and the booster antenna 402 having been reduced compared with thecontactless chip card module arrangement 410 shown in FIG. 4B, i.e. twosides of the off-chip coil 406 are over their entire length immediatelyadjoining and essentially in parallel with the booster antenna 402.Compared with the exemplary contactless chip card module arrangement 430shown in FIG. 4C, the exemplary contactless chip card module arrangement440 shown in FIG. 4D has a greater coupling parameter since in this casea larger section of the off-chip coil 404 (two sides) extendsimmediately adjoining the booster antenna 402.

FIG. 4E shows a further exemplary contactless chip card modulearrangement 440 in which the booster antenna 402 is arranged immediatelyadjoining and essentially in parallel with three sides of the chip cardmodule 404 along its complete length, the chip card module 402 beingarranged outside the booster antenna area.

By comparison, the booster antenna 402 is arranged immediately adjoiningand essentially in parallel with three sides of the chip card module 404along its complete length in the exemplary contactless chip card modulearrangement 450 shown in FIG. 4F, but the chip card module 404 isarranged here within the booster antenna area. In comparison with thechip card module arrangement 440 shown in FIG. 4E, a greater couplingparameter is obtained here. Using geometries of this type, couplingparameters of the order of magnitude of between 0.1 and 0.2 can beachieved in dependence on the number of turns of the booster antenna 402and the distance between these and the off-chip coil 406.

In summary, it can be concluded from the results in FIG. 4A to FIG. 4Fthat, on the one hand, the arrangement of the chip card module 404within the booster antenna area and, on the other hand, the smallestpossible distance between the off-chip coil 406 (or the turns formingthe off-chip coil 406, respectively) and the booster antenna 402 have apositive effect on the coupling parameter, i.e. increase it.Furthermore, the coupling factor grows with increasing number of sidesof the off-chip coil 406 which are arranged adjoining the boosterantenna 402. In this context, adjoining arrangement is understood to bean arrangement in which the distance between the booster antenna 402 andthe off-chip coil 404 is a few millimeters and is, for example, lessthan 4 millimeters.

As has already been found, apart from the number of turns of the boosterantenna according to various embodiments, the smallest possible distancebetween the turns of the booster antenna and the turns of the off-chipcoil is also an important parameter which can influence the couplingbetween booster antenna and off-chip coil. FIG. 5 shows a section of anembodiment of an inductive coupling area 500. The coupling area 500 isformed by a corner area of the booster antenna structure according tovarious embodiments. The off-chip coil is arranged adjoining one cornerof the booster antenna, i.e. two sides of an outer turn of turns 502 ofthe off-chip coil extend at a distance 506 essentially in parallel withthe turns 504 of the booster antenna. As an alternative to the caseshown in FIG. 5, the two distances 506 drawn in can also be different.

According to various embodiments, the turn conductor tracks can have awidth in a range of approximately 50 μm up to approximately 400 μm andbe, for example, about 100 μm. A turn conductor track width in the upperrange can result, for example, if the turn conductor track actsadditionally as an electrode of a plate capacitor.

In various embodiments, a booster antenna structure for a chip card isprovided, wherein the booster antenna structure has a booster antennaand an additional electrically conductive structure connected to thebooster antenna. In various embodiments, a booster antenna may beunderstood to be an amplifier antenna which supports or amplifies thesignal transmission between the chip card or the chip card module,respectively, and a reader. In this context, the chip card module mayhave a resonant circuit which may have essentially a chip card moduleantenna and the chip. The booster antenna may be an inductive structure,for example an arrangement of turns which may form, for example, a flatcoil. The coil may have, for example, a rectangular or polygonal shapeor a mixed shape of these, wherein the corners may be rounded. Theadditional electrically conductive structure may be a structureindependent of the booster antenna, i.e. a structure which provides anadditional ohmic impedance to the ohmic impedance of the structureswhich form the booster antenna. The booster antenna structure accordingto various embodiments may be optimized, for example, with respect toits electrical parameters and its geometry in such a manner that by thismeans ISO/IEC-compliant chip cards may be provided which also meet theEMVCo Standard.

According to various embodiments of the booster antenna structure, thebooster antenna and the additional electrically conductive structure mayjointly form an arrangement which has a resonant frequency ofapproximately 13.56 MHz. In other words, the booster antenna and theadditional electrically conductive structure may form a circuit, theresonant frequency of which is approximately 13.56 MHz. This frequencycorresponds to one of the RFID (radiofrequency identification) operatingfrequencies specified according to the ISO/IEC 18000 Standard. Theactual resonant frequency may deviate from 13.56 MHz due to componentparameter-related deviations from standard parameters. In variousembodiments, a deviation of up to about 10% may be considered asacceptable. The arrangement which has the booster antenna and theadditional electrically conductive structure can additionally have acapacitance.

According to various embodiments of the booster antenna structure, theadditional electrically conductive structure may have a meanderstructure. In various embodiments, the meander structure may have roundstructures or serrated structures or structures defined by corners. Themeander structure may have, for example, a serpentine shape, wherein theserpentine can have sections of different length between locations ofdirection changes. As well, at least one corner of the meander structuremay be rounded or the meander structure may have a zigzag shape. Themeander structure may be designed overall as a periodic structure oralso have a string of periodic conductor track sections. As analternative, the meander structure may have a shape free of symmetry.

According to various embodiments of the booster antenna structure, theelectrically conductive structure may also be provided as a discretecomponent, for example in the form of a line which has a differentmaterial in comparison with the lines to which it is connected.Furthermore, the electrically conductive structure may be arranged astapering of a line in at least one area of the booster antennastructure.

According to various embodiments of the booster antenna structure, theadditional electrically conductive structure may have, together with thebooster antenna structure, an ohmic impedance of at least 5 Ω, forexample 10 Ω, if the additional electrically conductive structure isinterconnected in series with the booster antenna. In the case of aparallel interconnection of the additionally conductor structure withrespect to the booster antenna, the impedance of the additionallyelectrically conductive structure may be, together with the boosterantenna structure, for example about 500 Ω. In serial interconnectionand in parallel interconnection, the booster antenna has differentequivalent impedances with respect to the additionally electricallyconductive structure. During the design of the booster antennastructure, the ohmic impedance of the entire structure must be takeninto consideration, that is to say, for example, impedance of thebooster antenna, of the additionally electrically conductive structureand, for example, of a capacitor. Compared with a direct-currentresistance, the frequency and the phase of the current or of the voltagemust be taken into consideration in the calculation of the resistance inthe case of an impedance so that the impedance can differ distinctlyfrom a direct-current resistance of an electronic component such as theadditional electrically conductive structure due to effects such asself-inductance, the so-called proximity effect or the skin effect. Theactual impedance of the additionally conductive structure can beadjusted, for example, by the choice of material and/or its shape.

According to various embodiments of the booster antenna structure, theadditional electrically conductive structure and the booster antenna maybe formed from different materials. The booster antenna can have, forexample, materials such as Ag, Al, Cu, Au or alloys thereof As well, theadditionally electrically conductive structure can have these materials,independently of the materials selected for the booster antenna. Ingeneral, the choice of material can be adapted taking into considerationthe shape and the dimension of the additionally electrically conductivematerial so that a desired resistance value can be set.

According to various embodiments of the booster antenna structure, theadditional electrically conductive structure and the booster antenna maybe coupled to one another in series. As an alternative, according tofurther various embodiments, the additional electrically conductivestructure and the booster antenna can be coupled to one another inparallel.

According to various embodiments, the booster antenna may have at leastone inductive coupling area and be constructed as resonant circuit. Theinductive coupling area may be arranged for coupling the booster antennato a further antenna, for example to a chip card module antenna arrangedon a chip card module. By means of the at least one inductive couplingarea, the booster antenna may be coupled inductively to the chip cardmodule antenna or to the chip card module, respectively, so that nomechanical contacts need to be provided between these two.

According to various embodiments, the booster antenna structure mayfurther have a capacitor. The capacitor may be connected to the boosterantenna and form in such an arrangement, together with the boosterantenna and the additionally electrically conductive structure, aresonant circuit.

According to various embodiments of the booster antenna structure, thecapacitor may be formed as a plate capacitor. The individual capacitorplates may be constructed on the same side or on different sides of afoil or of a carrier on which the booster antenna structure is arranged.Between the capacitor plates, a dielectric can also be arranged.Generally, the capacitor may have two mutually electrically insulatedconductor strings arranged at a distance from one another, wherein theoverall structure may have any shape. Thus, the plate capacitor may bepresent, for example, rolled together to form a spiral shape, eachspiral string corresponding to one of the capacitor electrodes. Thecarrier or the carrier layer may have generally an electricallyinsulating material, for example a plastic or a plastic laminate, and bepresent as a foil or as a thin layer of material.

According to various embodiments of the booster antenna structure, thecapacitor may have a number of lines arranged next to one another inparallel, wherein every second line is connected to the same capacitorelectrode. For example, each of the capacitor electrodes may have afinger structure, the capacitor electrodes being rotated by 180° withrespect to one another and arranged in such a manner that at least onefinger of one capacitor electrode is arranged between two fingers of theother capacitor electrode, the fingers of the two capacitor electrodesbeing electrically insulated from one another.

According to various embodiments of the booster antenna structure, thestructures which form the capacitor, and the booster antenna structure,may be arranged in the same plane. In this case, no additionalstructural layer is required in which one of the components is arrangedseparately, but both the structures forming the capacitor and thebooster antenna structure may be formed in a forming process on the samelayer, i.e. in the same plane, that is to say, for example, on one or ontwo sides of the carrier on which the booster antenna structure isarranged. The capacitor may also be configured as line capacitor andarranged, for example, as dummy turn. The dummy turn may have twoconductor tracks extending next to one another, the winding direction ofthe two conductor tracks being opposite with respect to one another sothat the dummy turn does not supply any or a negligible contribution tothe inductance of the booster antenna structure.

In various embodiments, a contactless chip card module arrangement isprovided having a booster antenna structure according to variousembodiments and a contactless chip card module which has a chip and acoil which is electrically coupled to the chip, wherein the boosterantenna structure may be inductively coupled to the coil of thecontactless chip card module by means of at least one inductive couplingarea of the booster antenna. The inductive coupling of the coil of thecontactless chip card module with the booster antenna structure can beachieved by positioning the coil in the vicinity of the booster antenna.In this context, individual areas of the turns of the chip card modulecoil which may have, for example, a rectangular or polygonal shape, mayextend adjoining the booster antenna on one or more sides. The chip cardmodule arrangement may form a part of a chip card which, for example,meets the ISO/IEC 7810 Standard. In various embodiments, the contactlesschip card module arrangement may additionally have a contact-basedinterface, for example in the form of chip card contacts arranged on thechip card module, by means of which the contactless chip card modulearrangement can also communicate contact-based with a reading unit. Dueto the electrical or inductive coupling between booster antenna and chipcard module antenna, it is not required to form an electrical bodycontact between the booster antenna and chip card module antenna whichalso requires precise milling in the chip card or the chip card body,respectively.

According to various embodiments of the contactless chip card modulearrangement, the booster antenna structure may be power-matched to thecontactless chip card module, wherein the match may be adjustable bymeans of the additional electrically conductive structure. Such powermatching provides for optimum power transmission of signals or energybetween the booster antenna structure and the contactless chip cardmodule and can be achieved, for example, by adapting the resistance ofthe additionally conductive structure to a transformed resistance of thechip card module, the transformed resistance of the chip card modulebeing discussed in greater detail later.

According to various embodiments of the contactless chip card modulearrangement, the at least one inductive coupling area of the boosterantenna can have a structure enclosing the coil of the contactless chipcard module. In this context, the enclosing structure can have anintegral part of the booster antenna in the form of an output orextension of a turn of the booster antenna which can then also form acoil which, for example, can surround the coil of the chip card module.

According to various embodiments of the contactless chip card modulearrangement, the enclosing structure can have at least two turns whichenclose the coil of the contactless chip card module. The at last twoturns can then be arranged at an equal distance from all sides of thecoil of the chip card module. The distance between the turns of theenclosing structure and at least one side of the coil of the chip cardmodule can be different, however, from the distances between the turnsof the enclosing structure and the remaining sides of the coil of thechip card module.

According to various embodiments of the contactless chip card modulearrangement, the at least one inductive coupling area of the boosterantenna can be arranged in a corner area of the booster antenna. Thecorner area of the booster antenna can have here two sides, wherein eachside can extend adjoining and essentially in parallel with one side ofthe coil of the contactless chip card module.

According to various embodiments of the contactless chip card modulearrangement, the at least one inductive coupling area of the boosterantenna can be located within an area which is bounded by conductortracks forming the booster antenna. This can be the case, for example,if the coil of the contactless chip card module is arranged in an innercorner or at an inner side of the booster antenna, wherein the innerside of the booster antenna can be specified by a turn of the boosterantenna coil which is located completely inside. The at least oneinductive coupling area can be designed in such a manner that the coilof the contactless chip card module is surrounded essentially alongthree of its sides by turns of the booster antenna and the at least oneinductive coupling area is formed as a type of bay, as it were.

According to various embodiments of the contactless chip card modulearrangement, the at least one inductive coupling area of the boosterantenna may be located outside an area which is bounded by conductortracks forming the booster antenna. This can be the case, for example,if the coil of the contactless chip card module is arranged at an outerside of the booster antenna, wherein the outer side of the boosterantenna may be specified by a turn of the booster antenna coil which iscompletely located on the outside. In this context, the at least oneinductive coupling area can be formed in such a manner that the coil ofthe contactless chip card module is surrounded essentially along threeof its sides by turns of the booster antenna and the at least oneinductive coupling area is formed as a type of bay, as it were.

In various embodiments, a contactless chip card module arrangement isprovided having a booster antenna structure according to variousembodiments and a contactless chip card module which has a chip and acoil which is coupled electrically to the chip, wherein the boosterantenna structure may be coupled inductively to the coil of thecontactless chip card module and wherein the electrically conductivestructure external to the booster antenna, together with the boosterantenna structure, has an ohmic impedance, the value of which resultsfrom an operating frequency of the chip, the inductance of the boosterantenna and the quality of the booster antenna. In this context, thebooster antenna structure may be power-matched to the contactless chipcard module. The power matching may be adjustable, for example by meansof an adaptation of the booster antenna-external electrically conductivestructure, for example a booster antenna resistance. During theadaptation of the ohmic impedance of the booster antenna-externalelectrically conductive structure, the quality of the booster antennamay also be set and by this means the reaction of the contactless chipcard module arrangement to a reading unit can be adjusted. In variousembodiments, the booster antenna-external electrically conductivestructure may be understood to be a structure which is not a componentof the coil turns of the booster antenna but represents an electricallyconductive structure which is additional to the turns of the boosterantenna, which may be interconnected in parallel or in series with thecoil or the turns, respectively, of the booster antenna.

According to various embodiments of the contactless chip card modulearrangement, the contactless chip card module may also have chip cardcontacts which are configured for providing a contact-based chip cardinterface. The chip card contacts may form a contact field whichcorresponds to the ISO/IEC 7816 Standard. The contact field can have sixor eight individual chip card contacts which may have normal conductivematerials.

According to various embodiments of the contactless chip card modulearrangement, the contactless chip card module arrangement may beconfigured as a dual interface chip card module arrangement. Thecommunication with the chip of the dual interface chip card modulearrangement may then take place optionally by means of the contact-basedinterface in the form of the chip card contacts or by means of thecontactless interface in the form of the chip card module antenna andthe booster antenna. A dual interface chip card may have a chip cardmodule which may have a chip and a coil in the form of conductor trackturns which assumes the function of an antenna and provides for thecontactless communication. The joint arrangement of the coil and of thechip on one chip card module is also called CoM (coil on module). Theinterconnection of the chip and of the coil on the chip card module of adual interface chip card represents a resonant circuit which may beoperated independently.

The chip card in which the booster antenna structure and/or thecontactless chip card module arrangement may be used may be, forexample, a chip card which is compliant with the ISO/IEC 7810 Standard.Accordingly, the chip card may have each of the normal size formatsID-1, ID-2, ID-3, ID-000 (also called mini-SIM format, SIM: SubscriberIdentity Module) or 3FF (also called micro-SIM format). Depending on thesize of the chip card, it may also have more than one chip card module.For example, two chip card modules may be arranged on one chip card sothat the chip card may be inserted with one of its ends into a reader orpulled through such a one and the user can thus select which chip cardmodule is to be used. In this case, each chip card module antenna may bearranged in a separate inductive coupling area.

The influence of the distance between the turns 502 of the off-chip coiland the turns 504 of the booster antenna on the strength of coupling orthe coupling parameter k, respectively, is shown in diagram 600 in FIG.6. The coupling parameter is plotted along the x axis 602 of diagram 600and the distance 506 drawn in FIG. 5 is plotted along the y axis 604.The coupling parameter may be understood in various embodiments to be ameasure in which a current flowing through particular turns (off-chipcoil or booster antenna) is capable of inducing a current flow in theother turns (booster antenna or off-chip coil). From curve 606 indiagram 600, it may be seen that the coupling parameter k becomes eversmaller the greater the distance 506 between the outer one of turns 502of the off-chip coil and the adjoining turn of turns 504 of the boosterantenna.

FIG. 7 shows a section of a booster antenna structure 700 according tovarious embodiments. The at least one inductive coupling area 706,within which an off-chip coil of a chip card module may be arranged, isformed in this case by coupling turns 704 or surrounded by these,respectively. The coupling turns 704 may be formed by an extended turnof the turns 702 of the booster antenna, wherein their number can bewithin a range of between one and approximately five depending on theexisting space and desired strength of coupling and may be, for example,three. Using such geometries, the highest strengths of coupling, whichcan be within a range of from 0.2 to 0.3, may be achieved in dependenceon the number of coupling turns 704, the number of turns 702 of thebooster antenna and/or the distance of the turns of the off-chip coilfrom the coupling turns. The case may also occur in which an overlap canoccur between the chip card module antenna of the chip card module andthe booster antenna on at least one of the sides if, for example, thearea of the chip card module antenna is greater than the inductivecoupling area which is fixed by the coupling turns 704.

Further embodiments of the at least one inductive coupling area areshown in each case in FIG. 8A and FIG. 8B. In both figures, a section ofa contactless chip card module arrangement 800 according to variousembodiments is shown which has the at least one inductive coupling area806. Within the at least one inductive coupling area 806, the chip cardmodule 804 is arranged on which the chip 810 surrounded by the off-chipcoil 808 is located. The at least one inductive coupling area 806 isformed by parts of the booster antenna 802 both in FIG. 8A and in FIG.8B. In both figures, booster antenna 802 is shown simplified by only oneturn; naturally, there can be further turns. As in FIG. 7, for example,the inner turn can have a part-piece which is constructed to form asmall coil in the form of small turns which border the at least oneinductive coupling area 804 as shown in FIG. 8A and in FIG. 8B, whereinthe turns enclosing the at least one inductive coupling area 804, indeviation from the presentation in the figures, also have roundedcorners and/or have a round, oval or polygonal shape. The distancebetween each of the sides of the chip card module 806 or the off-chipcoil, respectively, from the sides of the inner turn of the at least oneinductive coupling area 806 can be different for at least one of thesides. In other words, the chip card module 804 does not need to bearranged centrally or symmetrically within the at least one inductivecoupling area 806. In FIG. 8A and in FIG. 8B, the arrows show a possibledirection of current flow within the booster antenna 802. In theembodiment shown in FIG. 8A of the booster antenna structure 800, thedirection of current flow within the booster antenna 802 or within itsturns, respectively, matches the direction of current flow within thesmaller turns enclosing the at least one inductive coupling area 804. Inother words, the direction of the electromagnetic field which isgenerated by current flow through the turns of the booster antenna 802without taking into consideration the at least one inductive couplingarea 806 matches the direction of the electromagnetic field which isgenerated by the current flow through the smaller turns enclosing the atleast one inductive coupling area 806. In the embodiment shown in FIG.8B of the booster antenna structure 800, the direction of current flowwithin the booster antenna 802 or within its turns, respectively, doesnot match the direction of current flow within the smaller turnsenclosing the at least one inductive coupling area 804, the directionsof current flow are opposite one another in this case. In other words,the direction of the electromagnetic field which is generated by currentflow through the turns of the booster antenna 802 without taking intoconsideration the at least one inductive coupling area 806 is arrangedopposite the direction of the electromagnetic field which is generatedby current flow through the smaller turns enclosing the at least oneinductive coupling area 806. Furthermore, it must be noted that bothalternatives provide good inductive coupling of the booster antenna 802with the chip card module 804 or the off-chip coil 808, respectively.

In the case of the embodiments of the booster antenna structure, shownin FIG. 8A and in FIG. 8B, the sensitivity of the accuracy ofpositioning of the chip card module 804 within the at least oneinductive coupling area 806 has been investigated. As a result, it hasbeen determined that deviations of up to about 1.5 mm of the chip cardmodule in one of the three spatial directions from its specifiedposition can scarcely be detected, that is to say system variables suchas response field strength or load modulation amplitude change onlyinsignificantly. From a deviation of about 2 mm of the chip card modulein one of the three spatial directions from its predetermined position,changes can be detected which, however, still provide for correctoperation of the contactless chip card module arrangement. Overall, itcan be concluded from this that the contactless chip card modulearrangement according to various embodiments is insensitive todisplacements or positioning errors of the chip card module with respectto the booster antenna structure which can considerably simplify theproduction of a corresponding chip card which can have the contactlesschip card module arrangement according to various embodiments.

FIG. 9 shows a circuit diagram 900 of a system having a reading unit 902(also called PCD (proximity coupling device)) and a contactless chipcard module arrangement 904 (also called PICC (proximity integratedcircuit card)) according to various embodiments. The reading unit 902has a reading unit antenna 910 which can be formed as a coil. Thecontactless chip card module arrangement 904 which, for example, can bepart of a contactless chip card or of a dual interface chip card has achip card module 908 and a booster antenna structure 906. The chip cardmodule 908 has an off-chip coil 918 which is connected to the chip whichis modeled by a parallel circuit of an on-chip capacitor 920 and anon-chip resistor 922, the latter representing the ohmic consumption ofthe chip. The on-chip capacitor 920 can also represent a (parasitic)capacitor, connected in parallel with the on-chip coil 918, of the chipcard module antenna and/or an off-chip capacitor. In addition, a furtherresistor can be connected in series with the off-chip coil 918. Thebooster antenna structure 906 is represented by a resonant circuit inthe form of a series circuit which has a booster antenna coil 912, abooster capacitor 914 and an additional electrically conductivestructure, for example a booster resistor 916. In the circuit of thebooster antenna structure 906, the booster resistor 916 may also beconnected alternatively in parallel with the arrangement which has thebooster antenna coil 912 and the booster capacitor 914. The threepart-systems may be coupled electromagnetically to one another. A firstarrow 926 identifies the electromagnetic coupling between the boosterantenna structure 906 and the off-chip coil of the chip card module 908,the second arrow 924 identifies the electromagnetic coupling between thebooster antenna structure 906 and the reading unit 902 and a third arrow928 identifies the electromagnetic coupling between the reading unit 902and the off-chip coil 918 of the chip card module 908.

One of the aims in designing the booster antenna structure can consistin reducing the reaction effect below a certain limit which can begiven, for example, by the ISO/IEC 10373-6 Standard or by the EMVcontactless communication protocol specification 2.0.1, withoutincreasing the required minimum operating field strength in doing so.The reaction effect may be reduced, for example, by reducing the qualityfactor of the booster antenna which results from the product of theoperating frequency and the inductance of the booster antenna coil 912divided by the booster resistance 916. The reduction in the qualityfactor can be achieved by increasing the booster resistance 916 and afurther resistance which results from a transformation of the chip cardmodule circuit 908 into the booster antenna structure circuit 906 due tothe electromagnetic coupling between booster antenna 912 and theoff-chip coil 918. In the case where the resonant frequency of theresonant circuit which has the chip card module antenna and the chip,corresponds to the operating frequency, this transformed resistance ofthe chip card module R_(Mtr) is obtained as

${R_{Mtr} = \frac{R_{IC}k_{BM}^{2}L_{B}}{L_{M}}},$

where R_(IC) corresponds to the on-chip resistance 922, k_(BM)corresponds to the strength of coupling 926 between the booster antennastructure 906 and the off-chip coil 918, L_(B) corresponds to theinductance of the booster antenna coil 912 and L_(M) corresponds to theinductance of the off-chip coil 918. A normal on-chip resistance R_(IC)can be, for example, 1 kiloohm, a normal inductance of the off-chip coilcan be, for example, 2.4 microHenry.

The sum of the booster resistance 816 and the transformed resistance ofthe chip card module R_(Mtr) corresponds to a total resistance R_(total)which determines the reaction effect. In the case of chip cards in theID-1 format (according to ISO/IEC 7810 Standard), the total resistanceR_(total) can be, for example, approximately 65 ohms. To achieve powermatching between the chip card module and the booster antenna structure,the transformed resistance of the chip card module R_(Mtr) and thebooster resistance 916 can be selected to be approximately equal. Thismakes it possible that an optimum of power can be transferred betweenchip card module and booster antenna. The booster resistance 916 can beadapted, for example, via the width of the turn conductor tracks of thebooster antenna 912 and/or by means of a suitable choice of the totallength of the booster antenna 912 without the inductance of the boosterantenna 912 and the booster antenna area, i.e. the area which isbordered by the booster antenna turns, being changed significantly.

The aspect of power matching between chip card module and boosterantenna is clarified by means of FIG. 10 which shows an equivalentcircuit diagram of a contactless chip card module arrangement 1000having a chip card module antenna, a chip and a booster antennaaccording to various embodiments. A reading unit can induce in thebooster antenna a voltage which is shown as voltage source 1002 in theequivalent circuit diagram of the contactless chip card modulearrangement 1000. The voltage source 1002 has a voltage generator 1006which represents the induced voltage, and an internal impedance 1008which takes into consideration the ohmic resistance of the boosterantenna structure. The inductive coupling between booster antenna andchip card module antenna within the contactless chip card modulearrangement 1000 according to various embodiments is taken intoconsideration here by means of an equivalent T circuit which has a firstinductance 1014 (M_(BM)), a second inductance 1012 (L_(B)-M_(BM)) and athird inductance 1016 (L_(M) -M_(BM)). The contactless chip card modulearrangement 1000 which can be, for example, a part of a contactless chipcard or of a dual interface chip card, has a chip card module and abooster antenna structure which are shown as one unit for simplificationin the circuit diagram in FIG. 10. The chip card module has an off-chipcoil which is represented in the third inductance 1016 which isconnected to the chip which is modeled by means of a parallel circuit ofan on-chip capacitance 1018 and an on-chip resistance 1020. The boosterantenna structure is modeled by a series circuit which has a boosterantenna coil which is represented in the second inductance 1012, theresistance 1008 and a booster capacitance 1010.

Normal chip card systems with inductive coupling between a chip cardmodule and a booster antenna do not meet the requirements of relevantperformance standards for chip cards such as EMVCo and/or ISO/IEC10373-6. One possibility of solving this problem consists in optimizingthe power transfer by selectively matching the booster antenna to thechip card module which has the chip card module antenna and the chip.

Optimizing the power transfer can involve a number of aspects. On theone hand, the resonant chip card module circuit (e.g. see chip cardmodule circuit 908 in FIG. 9), which essentially has the chip and theoff-chip coil, can be set to the operating frequency of the chip forthis purpose which can be, for example, at 13.56 MHz. The resonantfrequency of the resonant chip card module circuit can be adjusted, forexample, by means of adapting the inductance of the off-chip coil and/orby providing an additional off-chip capacitance. On the other hand, theresonant frequency of the booster antenna circuit (e.g., see boosterantenna circuit 906 in FIG. 9) can also be set to the operatingfrequency of the chip, that is to say, for example, to 13.56 MHz. Theresonant frequency of the booster antenna circuit can be adjusted, forexample, by means of the additional electrically conductive structureconnected to the booster antenna or by means of a capacitance.Furthermore, the quality factor of the booster antenna can be determinedand adapted by means of the additionally electrically conductivestructure (e.g. booster resistance 916 in FIG. 9) in such a manner thatit corresponds to the real component of a complex impedance (see compleximpedance Z in FIG. 10) which corresponds to the electrical impedancewhich is produced by introducing a chip card with a contactless chipcard module arrangement into the electromagnetic field of the antenna ofthe reading unit in its circuit. In other words, by adjusting thequality factor of the booster antenna, for example by means of theadditionally electrically conductive structure, the reaction effect ofthe booster antenna structure on the reading unit can be adjusted sothat a maximum standardized effect of reaction on the reading unit orthe antenna of the reading unit, respectively, is not exceeded. At thesame time, the power matching between the booster antenna and the chipcard module or the off-chip coil, respectively, provides for operationat a working field strength required as standard. Overall, it ispossible to say that the booster antenna structure can be adaptedindividually for various chip cards as a result of which relevantstandards for contactless systems can be met.

As already mentioned, a capacitor may be provided in the booster antennastructure for adjusting the resonant frequency of the booster antennawhich can lie, for example, at 13.56 MHz. The capacitor may be producedin various ways. If both surfaces of the layer are available in which oron which the booster antenna structure is formed (called carrier layerin the text which follows), the capacitor may be formed, for example, inthe form of a plate capacitor, where one plate each can be arranged onone surface in each case. If the capacitor is to be formed on only oneof the surfaces, capacitors may be provided which have conductor tracksextending adjacent to one another which have, for example, a fingerstructure or a spiral structure. In each case, the required capacitancevalue C_(B) of the capacitor may be calculated as follows:

${C_{B} = \frac{1}{\left( {2\pi \; f_{res}} \right)^{2}L_{B}}},$

where f_(res) is the resonant frequency of the circuit and L_(B) is theinductance of the booster antenna.

The capacitance C of plate capacitors in which the capacitor plates arearranged on different sides of the carrier layer is obtained, on the onehand, from the area A of one of the plates or electrodes of thecapacitor and, on the other hand, from the thickness d and thedielectric conductivity c of the layer or of the substrate on which thebooster antenna is arranged:

$C = {ɛ{\frac{A}{d}.}}$

FIG. 11A shows a possible embodiment of a capacitance 1104 of thebooster antenna structure 1100 which has a finger shape (fingercapacitor in the text which follows) and is connected in series with thebooster antenna 1102, the booster antenna 1102 being represented here byonly one turn, by way of example. An enlarged view of the fingercapacitor 1104 is shown in FIG. 11B. The finger capacitor 1104 has afirst electrode 1106 and a second electrode 1108 which in each case havea comb-like or finger-like structure and form a so-called interdigitalstructure. In other words, the electrodes have a number of conductortracks extending in parallel next to one another, one conductor track ofthe other electrode being arranged in each case between two conductortracks each of one electrode. The capacitance may be adjusted, forexample, by means of a suitable number of the conductor track fingersper electrode and/or the proportion by which the fingers of the twoelectrodes overlap or are pushed into one another and/or the size of thefree spaces between the fingers of an electrode and/or by providing adielectric material between the fingers and/or the dimension of theconductor tracks forming the fingers, i.e. the dimension of the crosssectional area of the conductor tracks forming the fingers.

A further possible form which the capacitance can have is shown in FIG.12A. To illustrate, the booster antenna structure 1200 is here alsorepresented by only one turn 1202 and connected to a spiral capacitor1204. A spiral capacitor 1204 may be understood in various embodimentsto be a capacitor which has two conductor tracks forming a conductortrack string and extending next to one another, the conductor trackstring being rolled together to form a spiral. In this arrangement, thespiral does not need to have a circular shape, it can also be oval or apolygon having rounded corners. The capacitance value of the spiralcapacitor is adjustable, for example by adapting parameters which havealready been mentioned in conjunction with the finger capacitor.

Another further possible shape which the capacitance can have is shownin FIG. 12B. The booster antenna structure 1210 has three turns 1212 inthis case. Furthermore, the end of the inner turn of the turns 1212 ofthe booster antenna structure 1210 is followed by an inductive couplingarea 1216 which is surrounded by coupling turns 1218. The, for example,three coupling turns 1218 are here formed from an extension of one endof an inner turn of the turns 1212 of the booster antenna structure1210. The end of the conductor track formed by the coupling turns 1218is followed by a dummy turn 1214 which forms the capacitor. The dummyturn 1214 has two conductor tracks extending in parallel next to oneanother, the first conductor track 1220 being coupled to the end of theconductor track which forms the coupling turns 1218 and the secondconductor track 1222 being coupled to the end of the outer turn of theturns 1212 of the booster antenna structure 1210. The first conductortrack 1220 and the second conductor track 1222 have an oppositedirection of circulation with respect to one another. The ends of thefirst conductor track 1220 and of the second conductor track 1222 areopen or are not connected to any other structure analogously to the endof the conductor track double string which forms the spiral capacitance1204 in FIG. 12A. The double string which is formed by the firstconductor track 1220 and the second conductor track 1222 as such has twoturns, wherein its course can deviate from the course shown in FIG. 12Band can be matched to unoccupied areas in the plane of the boosterantenna structure 1210 or to areas to be kept free which, for example,are reserved for embossed lettering.

FIG. 13A shows an embodiment of a front or top 1300 and FIG. 13B showsan embodiment of a bottom or rear 1320 of a booster antenna structure.The embodiment is based on a two-sided design, i.e. a design formed onboth surfaces of the carrier layer 1310 on which the booster antennastructure is arranged. The embodiment shown in FIG. 13B and FIG. 13B ofa booster antenna structure may be produced, for example, by printingconductive structures on the substrate 1310 or by means ofelectroplating, but analogous structures may also be produced by meansof an etching process. On the basis of the considerations presentedhere, an antenna booster structure according to various embodiments or acontactless chip card module arrangement according to variousembodiments may be produced cost-effectively which meets the ISO/IEC14443 Standard and/or the ISO/IEC 10373-6 Standard and/or the EMVCoStandard, taking note of the areas reserved for embossing.

The embodiment of a booster antenna structure shown in FIG. 13A and FIG.13B may have a carrier layer or a carrier substrate 1310 which can have,for example, PVC. The substrate 1310 can have the size of a chip card inID-1 format (80 mm×48 mm) The structures arranged thereon can bedistributed in such a manner that areas which are provided, for example,for embossing on the chip card, are kept free. In this embodiment, thebooster antenna 1302 has two turns—one on the front and one on the rearof the carrier layer 1310, each of these turns extending close to theedge of the carrier layer 1310 in order to be extended essentially overthe entire size of a chip card. The turn on the front 1300 of thebooster antenna structure is connected to the turn on the rear 1320 ofthe booster antenna structure by means of through-contacting 1312. Apartfrom the two main turns, the booster antenna has additionally twocoupling turns 1308 which are also arranged on both sides of the carrierlayer 1310 and surround the at least one inductive coupling area 1304.In the embodiment shown in FIG. 13A to FIG. 13C, the through-contacting1312 connects the ends of the coupling turns 1308 to one another throughthe carrier layer 1310, these ends being connected in each case on thefront 1300 and the rear 1320 of the booster antenna structure to one endof the turn of the booster antenna 1302. The way in which the couplingarea 1304 is formed corresponds essentially to the principle alreadyshown in conjunction with, for example, FIG. 7. Furthermore, anelectrode of a plate capacitor 1306 is arranged on each surface of thecarrier layer 1310. The electrodes are arranged above one another on thedifferent sides or surfaces of the carrier layer 1310 and haveessentially a distance from one another which corresponds to thethickness of the substrate 1310. With an inductance of the boosterantenna coil 1302 of, for example, two microHenry, the couplingparameter between the off-chip coil (not shown) and the booster antenna1302 may be approximately 0.2. The total resistance R_(total) may be 65Ohms so that both the booster resistance and the transformed resistanceof the chip card module R_(Mtr) should be approximately 32 ohms for thepurpose of power matching. Furthermore, an electrically conductivestructure 1314 which has a meander shape is coupled to one another inseries with the coupling turns 1308 within the booster antennastructure. In this embodiment, the first additional electricallyconductive structure 1314 is arranged on the front 1300 of the boosterantenna structure. As an alternative, it may also be arranged on therear 1302 of the booster antenna structure.

FIG. 13C shows a booster antenna structure 1340, showing here the frontor top, respectively, 1300 from FIG. 13A and the bottom or rear,respectively, 1320, from FIG. 13B in a superimposed view.

In order to provide a correspondingly dimensioned additionallyelectrically conductive structure in the form of the booster resistor, atechnology can be selected for its production which normally exhibits ahigher resistance in conjunction with small conductor track widths suchas, for instance, a printing process in which functional electronicmaterials present in liquid or pasty form may be printed onto thecarrier layer 1310. Furthermore, the conductor track width and theconductor track thickness, that is to say the conductor track crosssection, can be reduced until the desired resistance value is achieved.The length of the booster antenna or its turns, respectively, can alsobe extended in such a manner that the other parameters of the boosterantenna, for example the inductance of the booster antenna, are notsignificantly changed. In the embodiment of the booster antennastructure shown in FIG. 13A and FIG. 13B, the thickness of its conductortracks can be 5 μm and the width of its conductor tracks can be 100 μmin order to achieve a resistance value of about 32 ohms when using anetching technique with copper as the conductive material. The preciseparameters may be determined by accurate measurement of the resistanceand/or the effect of reaction on a reading unit. The resonant frequencymay be adjusted in a simple manner, for example by trimming the platesof the capacitor 1306 with a cutting tool until the desired resonantfrequency of, for example, 13.56 MHz is reached.

The booster antenna structure according to various embodiments can beformed by means of various production methods. However, variousproduction methods have a different effect on electrical characteristicsof the booster antenna structure. This means that it may be necessary toproduce a separate design for each of the different production methodsin order to produce a particular booster antenna structure according tovarious embodiments. In other words, a booster antenna structure whichis identical with respect to operating parameters can be formed fromvarious designs since different production methods have differenteffects on electrical characteristics of electrical structures.Furthermore, it should also be taken into consideration that indesigning the booster antenna structure for a chip card in ID-1 format,certain areas are not available for the booster antenna structure suchas, for instance, a chip cavity into which the chip card module isinserted and/or areas which are reserved for embossing according to theISO/IEC 7811-1 Standard.

Booster antennas are available which are constructed in printed form.The design does not take into consideration the areas to be kept freeand it is questionable how it can be transferred to other productionmethods, if at all.

It is possible to investigate the different effect of differentproduction methods on the electrical characteristics of a boosterantenna structure. In this context, electrical components of the boosterantenna structure such as, for instance, capacitive and/or inductivestructures and/or the additionally electrically conductive structure canbe matched to the material and process characteristics of differentproduction methods in the equivalent circuit diagram. By understandingthe influence of various production methods on electricalcharacteristics of the booster antenna structure, prefabricated boosterantenna structure templates (inlay structures) of various manufacturerscan be utilized, on the one hand. On the other hand, the performance ofthe booster antenna structure according to various embodiments, and theyield in the production, can be optimized.

In the text which follows, specific design criteria are explained forvarious production methods. It is possible to define equivalent circuitdiagram parameters for each equivalent circuit diagram of an electricalstructure in the booster antenna circuit depending on the productiontechnology used.

In a production method which is effected by laying at least oneconductive conductor (wired technology), conductive structures of a wirecan be arranged on a substrate surface or carrier layer surface,respectively, wherein normal conductive materials such as copper,silver, aluminum, gold can be used as conductors. In this productionmethod, resistances, for instance the resistance of the additionallyelectrically conductive structure of the booster antenna according tovarious embodiments can be adjusted by a suitable choice of the materialand the diameter of a conductor used for the wiring. Furthermore, theconductor track length can also be adapted by forming, for example,meander-shaped wiring passages. Inductive structures can be produced bymeans of conductor tracks extending adjacently to one another, whereinthe value of the inductance can be adjusted via their distance from oneanother. Inductive structures can have, for example, turns, wherein thevalue of the inductance can be adjusted by means of their number andsize of the area bordered by them. Capacitive structures can be producedby line capacitances, for example in finger form or in spiral form.Furthermore, a capacitive structure can result in conjunction with ameander shape of the additional electrically conductive element.

In a production of the booster antenna structure by means of an etchingprocess or of an electroplating printing process in which the basicelectrical structures are initially printed on and then formed by meansof an electroplating process, the resistance, for instance theresistance of the additionally electrically conductive structure of thebooster antenna structure according to various embodiments, can beadjusted by the thickness and width of the conductor track, that is tosay its cross section, and by the material used. Similarly,meander-shaped structures can be formed for increasing the conductortrack length and thus the resistance. Inductive structures can beproduced by means of conductor tracks extending adjacently to oneanother, wherein the value of the inductance can be adjusted via theirdistance from one another. For example, inductive structures can haveturns, wherein the value of the inductance can be adjusted by theirnumber and the size of the area bordered by them. Capacitive structurescan be provided by a plate capacitance. For this purpose, separatelyformed capacitor electrodes in the form of plates can be formed, forexample, on the front and rear of the carrier substrate on which thebooster antenna is formed. Similarly, capacitive structures can beformed in the form of conductor tracks of the turns of the boosterantenna arranged above one another on the front and rear of the carriersubstrate. Furthermore, single-layer capacitive structures, that is tosay formed only on one of the surfaces of the carrier substrate, can beprovided, for example in finger form or in spiral form. A capacitivestructure can also be formed in conjunction with a meander form of theadditional electrically conductive element.

FIG. 14 shows an embodiment of a booster antenna structure 1400according to various embodiments which can be produced by means of anelectroplating printing process. The booster antenna structure 1400 canbe arranged on a carrier substrate 1410 which can have, for example, PVCand is provided with conductive structures on both sides. The carriersubstrate 1410 can have the size of a chip card in ID-1 format. One turneach of the booster antenna 1402 is arranged extending along the edge ofthe carrier substrate 1410 on the front and on the rear of the carriersubstrate 1410. Apart from these main turns, the booster antenna 1402additionally has smaller coupling turns which are also arranged on bothsides of the carrier substrate 1410 and enclose the at least oneinductive coupling area 1404. Furthermore, a first electrode of a firstplate capacitor 1406 and a first electrode of a second plate capacitor1408 is arranged on each surface of the carrier substrate 1410. Acorresponding second electrode of the first plate capacitor 1406 and acorresponding second electrode of the second plate capacitor 1408 isarranged on the other side of the carrier substrate 1410—the carriersubstrate 1410 acts here as a spacer between the two electrodes of theplate capacitors. If necessary, the carrier substrate 1410 can bethinned down at the locations of the plate capacitors if a distance isrequired between the capacitor plates of the first plate capacitor 1406and/or the second plate capacitor 1408 which is smaller than thethickness of the carrier substrate 1410. Furthermore, an additionalelectrically conductive structure 1412 is arranged on the carriersubstrate 1410 which is connected to the booster antenna structure 1400.The additional electrically conductive structure 1412 has a meander formwherein differently long meander areas can be contained within anadditionally electrically conductive structure 1412. The electricalstructures on both surfaces of the substrate 1410 are in electricalcontact with one another by means of feed-throughs 1414.

FIG. 15 shows an embodiment of a booster antenna structure 1500according to various embodiments which may be produced by means of anetching process. The exemplary booster antenna structure 1500 shown inFIG. 15 is similar to the exemplary booster antenna structure 1400 shownin FIG. 14 so that corresponding structures carry the same referencesymbols. Due to an etching process used for the production, however, thebooster antenna structure 1500 has a more filigree design compared withthe booster antenna structure 1400 which may be produced by means ofelectroplating printing processes.

A further possibility for producing a booster antenna structureaccording to various embodiments consists in using a printing process inwhich the basic electrical structures are completely printed on. Theresistance, for instance the resistance of the additionally electricallyconductive structure of the booster antenna according to variousembodiments can be adjusted in this production process by the thicknessand width of the conductor track, that is to say its cross section, andby the material used. Similarly, meander-shaped structures can be formedfor increasing the conductor track length and thus the resistance.Furthermore, a separate resistance element may be provided by using adifferent material which can be used for printing at one location in thecircuit of the booster antenna structure. Inductive structures may beproduced by conductor tracks extending next to one another, wherein thevalue of the inductance may be adjusted by their distance from oneanother. Inductive structures can have turns, for example, wherein thevalue of the inductance can be adjusted by their number and the size ofthe area bordered by them. Capacitive structures can be provided by aplate capacitors. For this purpose, separately formed capacitorelectrodes in the form of plates, for example, may be formed on thefront and rear of the carrier substrate on which the booster antenna isformed. Similarly, capacitive structures in the form of conductor tracksof the turns of the booster antenna arranged above one another on thefront and rear of the carrier substrate may be formed. Furthermore,single-layer capacitive structures, i.e. formed only on one of thesurfaces of the carrier substrate, may also be provided, for example inthe form of fingers or in spiral form. A capacitive structure can alsobe formed in conjunction with a meander-form of the additionalelectrically conductive element.

While the invention has been particularly shown and described withreference to specific embodiments, it should be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims. The scope of the invention is thusindicated by the appended claims and all changes which come within themeaning and range of equivalency of the claims are therefore intended tobe embraced.

1. A booster antenna structure for a chip card, wherein the boosterantenna structure comprises: a booster antenna; and an additionalelectrically conductive structure connected to the booster antenna. 2.The booster antenna structure as claimed in claim 1, wherein the boosterantenna and the additional electrically conductive structure jointlyform an arrangement which has a resonant frequency of approximately13.56 MHz.
 3. The booster antenna structure as claimed in claim 1,wherein the additional electrically conductive structure has a meanderstructure.
 4. The booster antenna structure as claimed in claim 1,wherein the additional electrically conductive structure has an ohmicimpedance of at least 5 Ω.
 5. The booster antenna structure as claimedin claim 1, wherein the additional electrically conductive structure andthe booster antenna are formed from different materials.
 6. The boosterantenna structure as claimed in claim 1, wherein the additionalelectrically conductive structure and the booster antenna are coupled toone another in series.
 7. The booster antenna structure as claimed inclaim 1, wherein the additional electrically conductive structure andthe booster antenna are coupled to one another in parallel.
 8. Thebooster antenna structure as claimed in claim 1, wherein the boosterantenna has at least one inductive coupling area.
 9. The booster antennastructure as claimed in claim 1, wherein the booster antenna structurefurther comprises a capacitor.
 10. The booster antenna structure asclaimed in claim 9, wherein the capacitor is formed as a platecapacitor.
 11. The booster antenna structure as claimed in claim 9,wherein the capacitor has a number of lines arranged next to one anotherin parallel, wherein every second line is connected to the samecapacitor electrode.
 12. The booster antenna structure as claimed inclaim 9, wherein structures which form the capacitor, and the boosterantenna structure, are arranged in the same plane.
 13. A contactlesschip card module arrangement, comprising: a booster antenna structurefor a chip card, wherein the booster antenna structure comprises: abooster antenna; and an additional electrically conductive structureconnected to the booster antenna; a contactless chip card module whichcomprises: a chip; and a coil which is coupled electrically to the chip;wherein the booster antenna structure is coupled inductively to the coilof the contactless chip card module by means of at least one inductivecoupling area of the booster antenna.
 14. The contactless chip cardmodule arrangement as claimed in claim 13, wherein the booster antennastructure is power-matched to the contactless chip card module; andwherein the power matching is adjustable by means of the additionalelectrically conductive structure.
 15. The contactless chip card modulearrangement as claimed in claim 13, wherein the at least one inductivecoupling area of the booster antenna has a structure enclosing the coilof the contactless chip card module.
 16. The contactless chip cardmodule arrangement as claimed in claim 15, wherein the enclosingstructure has at least one turn which encloses the coil of thecontactless chip card module.
 17. The contactless chip card modulearrangement as claimed in claim 13, wherein the at least one inductivecoupling area of the booster antenna is arranged in a corner area of thebooster antenna.
 18. The contactless chip card module arrangement asclaimed in claim 13, wherein the at least one inductive coupling area ofthe booster antenna is located within an area which is bounded byconductor tracks forming the booster antenna.
 19. The contactless chipcard module arrangement as claimed in claim 13, wherein the at least oneinductive coupling area of the booster antenna is located outside anarea which is bounded by conductor tracks forming the booster antenna.20. The contactless chip card module arrangement as claimed in claim 13,wherein the contactless chip card module also has chip card contactswhich are configured for providing a contact-based chip card interface.21. The contactless chip card module arrangement as claimed in claim 13,wherein the contactless chip card module arrangement is configured as adual interface chip card module arrangement.
 22. A contactless chip cardmodule arrangement, comprising: a booster antenna structure for a chipcard, wherein the booster antenna structure comprises: a boosterantenna; and an additional electrically conductive structure connectedto the booster antenna; a contactless chip card module which comprises:a chip; and a coil which is coupled electrically to the chip; whereinthe booster antenna structure is coupled inductively to the coil of thecontactless chip card module; wherein the electrically conductivestructure external to the booster antenna has an ohmic impedance, thevalue of which results from an operating frequency of the chip, theinductance of the booster antenna and the quality factor of the boosterantenna.
 23. The contactless chip card module arrangement as claimed inclaim 22, wherein the contactless chip card module also has chip cardcontacts which are configured for providing a contact-based chip cardinterface.
 24. The contactless chip card module arrangement as claimedin claim 22, wherein the contactless chip card module arrangement isconfigured as a dual interface chip card module arrangement.